This invention relates generally to the field of toner cartridges used in the dispensing of toner in particulate form used by electrostatic copiers, and more particularly, to an improved construction providing superior hopper capacity and feeding of toner particles to a dispensing opening.
In recent years, the performance of electrostatic copiers has been substantially improved from the aspect of copy and print quality. It has been found that when the image is formed of toner particles of smaller size, in the order of four microns, the resultant images are sharper, and there is less tendency to form image defects, such as ghosting, grain of white backgrounds, and the like. The most commonly used toners typically have a particle size averaging eight microns. With improved techniques, particle sizes are capable of reduction to particle size as little as five microns. With smaller particle size, the amount of toner used, a portion of which is wasted, is considerably reduced, as a result of which an individual toner cartridge may offer a substantially extended life cycle before replacement is necessary.
Unfortunately, the above-described smaller particle toner is not, at the present state of the art, capable of being manufactured at a cost comparable to that of the larger size particle toners. As a result, much of the replacement or re-manufactured toner cartridges are refilled with particulate toner of relatively larger sized particles, typically, eight microns.
It is possible, however, to extend the life cycle of such toner cartridges by increasing the toner capacity of the hopper contained within the toner cartridge. The size of the replacement hopper must, of course, conform to the available space within the toner cartridge and, as a result, in many cases, the hopper includes converging walls which are disposed at an angle considerably less steep with respect to the direction of toner flow when compared with the hopper which it replaces. Such configurations tend not to promote the flow of toner to the hopper discharge opening. In addition, most toners carry a static charge which tends to cause agglomeration, and also, a tendency to be attracted to the inner surface of the toner hopper. Where the walls of the toner hopper are considerably less steep, or more horizontal, the tendency of a substantial amount of toner to remain in the hopper at a distance from the point of discharge is substantially increased.